We were there during anniversary week in July last year. I was worried it was going to be awful- we found the crowds were very manageable. I wouldn't hesitate to go in July again. Heat is relative. I think it really depends on where you live and what you are used to. For us the temperature was great in the mornings and evenings, and a little hot for a few hours in the afternoon. There is not much humidity, so it felt a lot better to us that at home in the southern Midwest. We've been in early June and that time of year, we often get cold in the evenings and sometimes the mornings, but still hot in the afternoon. June is nice too- but if you are there the last week before a bunch of the passes are blocked during the week, that last Monday and Tuesday are really crowded- I would say the crowds those 2 days were definitely worse than what we experienced in July.